...does anyone know what happened to the P51D mustangs the Dominican airforce had?........
By 1984--when they were retired from service--the DR had only 10 (of the original 51 aircraft) airworthy P-51s remaining. Nine were sold to private collectors (and, from memory, there was some scandal attached to that episode) and one was kept by the Dominican Air Force and put on display. There could still be bits and pieces of P-51s scattered the the air force base.
The Haitians had six Mustangs given to them by the US. The P-51s were gradually withdrawn from service until the last Haitian P-51 was retired in 1974.
Four of the planes were sold to the DR for spare parts. Three of the planes had already been cannibalized by the Haitian Air Force for spare parts to keep the last one flying, so I doubt there was much left of them when they were sold to the Dominican Air Force.
The other two Haitian P-51s were purchased by an American collector (both were in extremely poor condition) and were fully restored in the United States and are flying again.